Arrangement for the testing of semiconductor structures

ABSTRACT

The present invention provides an apparatus for the testing of semiconductor structures. The apparatus is provided with a chuck for holding a semiconductor wafer and with needle holders for contact needles, the chuck being provided with a fastening device for the semiconductor wafer and being movable for positioning, controlled using a positioning device, in relation to the contact needles. The object of the present invention is to detect faults, in good time and reliably, of non-serviceable or not fully serviceable chips before separation to avoid unnecessary work for separating and assembling defective chips. The object is attained in that the chuck has a receiving area exposing upwards a lower surface of the semiconductor wafer and a receiving plane therefor. The receiving plane is arranged above the needle carrier, and the contact needles point upwards in such a manner that they contact contact islands of the semiconductor chips on the downwardly directed upper surface of the semiconductor wafer.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for testing semiconductorstructures, which is provided with a chuck for holding a semiconductorwafer which has a substantially unstructured underside and an upper sidewith structure of chips that are to be tested. The apparatus is providedwith several needle holders, for externally holding contact needleswhich are placed on contact islands of the chips to be tested. Moreover,the chuck is provided with contacting means for the semiconductor waferand is moved relative to the contact needles by a positioning device.

It is known that, for testing semiconductor chips, which are in a waferassembly on a semiconductor wafer, contact needles, which serve toconnect the semiconductor chips with an external test apparatus, may beplaced on contact islands of the chips.

For testing chips which are separated from the wafer assembly andassembled or pre-assembled into components, it is also known that theradiation behavior of the chips may be investigated. For this,photoemissions, which generally lie in the infrared region and aregenerated by a circuit structure of the chips during action ofelectrical voltage on the chips, are determined. Subsequently,malfunctions of the chip tested are detected, for example, by acomparison with radiation images of accurately operating comparisonchips or by means of generation of abnormal radiation.

To realize this test method, it is known that an infrared observationdevice may be used, which is directed towards an upper side of the chip.During a test, this infrared observation device is able to photograph aninfrared radiation image of the chip. It is able to portray and analyzeextremely weak light, which is generated particularly by malfunctioningof a semiconductor chip. Accordingly, for example, places on the chipcan be recognized, which generate heat radiation as a result of amalfunction, which have defective currents due to oxide breakdowns or ingate oxide layers or which do not show the specified emissions at PNtransitions, as a result of a malfunction. Such an infrared observationdevice can be constructed as an emission microscope or as a highlysensitive CCD camera.

However, arranging metal conductors on the chips, in some cases even inseveral layers, is being exploited increasingly frequently. Generally,these conductors are disposed in top layers of the chip, that is, closeto the surface. However, these conductors absorb or reflect thephotoemission described so strongly, that they prevent any observationof the extremely weak light radiation by an infrared observation device.

To avoid these disadvantages, it is known that the radiation behavior ofthe installed chip may be observed from a reverse side of the latter. Inthis connection, it is a disadvantage that, when a malfunction isdetected, the installed chip must be discarded. With that, the expenseof installing the chip, which is appreciable in some cases, is no longerof benefit.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to make it possibleto detect defects of non-serviceable or not fully serviceable chips ingood time and reliably before chip separation, in order to avoid anunnecessary expense of separating and installing defective chips.

Pursuant to the present invention, this objective is accomplished by achuck having a receiving area which exposes an underside of asemiconductor wafer in an upward direction, and a receiving plane forthe semiconductor wafer being disposed above a needle carrier havingcontact needles directed upward in such a manner as to contact thecontact islands of the semiconductor chips on the downwardly directedupper side of the semiconductor wafer.

The semiconductor wafer is inserted face-down in receiving area of thechuck. Since the semiconductor wafer lies in the receiving plane and,with that, above the needle carriers, and since the needles are directedupward, it becomes possible to contact the semiconductor chips frombelow. The receiving area exposes the underside of the semiconductorwafer upward, so that the underside can be observed from above.

In an appropriate embodiment of the present invention, provisions aremade so that the needle holder is fastened to a support which isstationary with respect to movement of a positioning device, such as anx-y mechanical stage, which moves the semiconductor wafer disposed inthe receiving plane.

To realize a relative movement between the chuck and the contactneedles, it is possible to move either the chuck or the contact needles.When the needle holder is stationary, a movement of the chuck isrealized. Since the chuck generally is the component with the lesserweight, a more rapid positioning of the contact needles is achieved.

It is particularly advantageous if fastening means for fastening thesemiconductor wafer are constructed as a mechanical and/or vacuumholding device. The semiconductor wafer is optionally clamped with amechanical fastening device. This can be realized with simple means. Onthe other hand, significantly larger holding forces can be achieved witha vacuum holding device, without causing damage to the semiconductorwafer. In practice, it may be advantageous to provide a mechanical aswell as a vacuum holding device. The mechanical holding device permitsthe semiconductor wafer to be held until the vacuum holding device acts.

In an advantageous embodiment, the mechanical fastening device includesa sliding block which, under action of a spring, engages an edge of thesemiconductor wafer in such a manner that a force of the spring pressesthe edge of the semiconductor wafer against opposite stops. When thesemiconductor wafer is inserted, the sliding block is simply pressedagainst the force of the spring and the semiconductor wafer insertedsubsequently. When the sliding block is released, the semiconductorwafer is clamped immediately.

In a different advantageous embodiment, which is optionally used incombination with a mechanical holding device, a suction surface, onwhich the upper side or the underside of the semiconductor wafer isplaced and which is provided with a suction groove connected to a vacuumsource, is provided as a vacuum holding device. When a semiconductorwafer is placed on the suction surface, the suction groove is closedoff, as a result of which the semiconductor wafer is attached by suctionand held therewith when a vacuum is applied.

Furthermore, it is advisable to provide the chuck with a spacer which isconnected to the x-y mechanical stage and sets a distance between thechuck and the x-y mechanical stage. The spacer makes it possible todispose components, such as the needle carriers, between the x-ymechanical stage and the chuck. With that, the conventional constructionof samplers can be maintained. An alternative includes, for example,initiating the x-y movement from outside, for example, from a remote x-ydriving mechanism.

It is particularly advantageous to dispose the positioning deviceunderneath the chuck. With that, all conventional positioning methodscan continue to be used, with the sole difference that a direction of anobservation device of the positioning device, which usually isconstructed as a camera, changes. However, this has little effect on thepositioning method.

To realize a spacing holder between the chuck and the needle holder, thechuck is constructed in plate fashion in such a manner, that it has thereceiving area for a semiconductor wafer and external brackets, disposedon either side of the receiving area, at outer ends of which bracketsthe spacers are fastened essentially perpendicularly to the brackets.

In a preferred embodiment of the present invention, the receiving areahas an opening with an opening surface, which is at least approximatelycongruent with a surface of the semiconductor wafer. An annular seat,which decreases an opening area, is provided at the opening on a bottomside of the chuck facing the contact needles. The seat is constructed asa suction surface and provided with an annular groove into which avacuum duct opens. Advisably, the seat touches only an edge of thesemiconductor wafer. With that, a remainder of the semiconductor waferstays free for contacting or for observation.

It is advisable to construct the vacuum holding device in such a mannerthat the vacuum duct is passed through the brackets and through thespacer, that a seat, into which the spacer can be inserted and in whichthe vacuum connection, which can be connected with the vacuum duct ofthe spacer, is disposed, is provided for a spacer.

As configured above, the chuck, after being equipped with asemiconductor wafer, is placed down and, at the same time, supplied witha vacuum.

A variation of the present invention includes a fastening plate with astructure for receiving a needle holder for testing the reverse side ofthe semiconductor wafer and with a structure for receiving an additionalreceiving plate for testing the upper side of the semiconductor wafer,which can be fastened with spacers to the fastening plate and on whichthe needle holders can be fastened, the contact needles being directedupward for testing the reverse side and downward for testing the upperside. Accordingly, needle holder can simply be removed from thefastening plate when the testing method is changed and fastened to thereceiving plate. In this case, the contact needles are changed withrespect to their direction of contact, that is, the contact needles nowcontact the contact islands of the semiconductor chips on the upwardlydirected upper side of the semiconductor wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail in thefollowing by means of an example. In the associated drawings,

FIG. 1a shows a plan view of a first embodiment of an apparatus of thepresent invention for testing a semiconductor wafer from below usingneedles;

FIG. 1b shows a front view of the first embodiment;

FIG. 2a shows a bottom view of a chuck of the first embodiment;

FIG. 2b shows a longitudinal side section view of the first embodiment;

FIG. 3a shows a plan view of a second embodiment of the presentinvention for testing a semiconductor wafer by means of contactingneedles engaging from above;

FIG. 3b shows a side view of the second embodiment;

FIG. 4a shows a plan view of a third embodiment of the present inventionfor testing a semiconductor wafer by means of a tester card engagingfrom below;

FIG. 4b shows a side view of the embodiment of FIG. 4a;

FIG. 5a shows a plan view of a fourth embodiment of the presentinvention for testing a semiconductor wafer by means of contactingneedles engaging from below and above;

FIG. 5b shows a front view of the fourth embodiment;

FIG. 6a shows a plan view of a fifth embodiment of the present inventionfor testing a semiconductor wafer by means of contacting needlesengaging from above and below and a tester card engaging from below; and

FIG. 6b shows a front view of the fifth embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1a and 1 b, an apparatus for testing semiconductorwafers has a base frame 1. A base plate 2 is connected via decouplingelements 3 to the base frame 1. An upper plate 4 is supported by aspacer 5 on the base plate 2.

A positioning device 6, which positions in a horizontal x direction anda horizontal y direction, is connected to the base frame 1. Thepositioning device 6 has a stage 7, onto which a chuck 8 is disposed.The chuck 8 serves to receive a semiconductor wafer 9 having a top side9 a and a bottom side 9 b as shown in FIG. 2b. For this purpose, anopening 14, of a receiving area 10, is provided in the upper side of thechuck 8 for exposing the bottom side 9 b of the wafer 9 to an infraredobservation device 34. Since the receiving area 10 is in the vicinity ofthe upper plate 4, that is, above the base plate 2, the chuck 8 amplyembraces the base plate 2, so that a transfer of movement of thepositioning device 6 to the chuck 8 is possible. For this purpose,brackets 11 are provided, which are on either side of the receiving area10 of the chuck 8. Spacers 12, which adjust a distance between the stage7 and the receiving plate 13 of the semiconductor wafer 9, are fastenedto outer ends perpendicularly to the brackets 11.

Referring to FIGS. 2a and 2 b, on an upper side, the chuck 8 isconstructed plate-shaped, the surface being at least parallel to thereceiving plane 13 of the semiconductor wafer 9. In the receiving area10, the chuck 8 is provided with an opening 14. A surface perimeter ofthe opening 14 is approximately congruent with the surface of thesemiconductor wafer 9, so that the semiconductor wafer 9 can be insertedin the opening 14. For fixing the semiconductor wafer 9, the opening 14is provided with an annular seat 15. An annular groove 16, which isclosed off by the semiconductor wafer 9 when seated, is in this annularseat 15. A vacuum duct 17, which passes through a bracket 11 andfurthermore through the spacer 12 and emerges at an end of the spacer12, opens out into the annular groove 16 and communicates with a vacuumopening in the stage 7. With that, vacuum suction for the semiconductorwafer 9 can be realized in the receiving area 10. A mechanical fasteningmeans is provided for provisionally fixing the semiconductor wafer 9before a vacuum is built up and includes a sliding block 18, which ismoved in a radial direction with respect to the opening 14 and parallelto the receiving plane 13 and which, under the action of a spring 30,engages the edge of the semiconductor wafer 9. With that, thesemiconductor wafer 9 is pressed against two pins 19, acting as stops,and thus fixed mechanically. This has the advantage that thesemiconductor wafer 9 can be inserted in the opening 14 and is alreadyfixed mechanically therewith. With the placement of the chuck 8 on thestage 7, the annular groove 16 is then acted upon by a vacuum, as aresult of which the semiconductor wafer 9 is attached by suction andheld.

By attachment by suction, on the one hand, the semiconductor wafer 9 isfixed in position and, on the other, contacting forces can be absorbedtherewith when the semiconductor wafer 9 is contacted on the side, onwhich it is also held. As shown in FIGS. 1a and 1 b, the base plate 2serves for receiving needle holders 20, which carry contact needles 21.If now upwardly directed the contact needles 21 are inserted in theneedle holder 20, the contact needles 21 engage contact islands on thesemiconductor wafer 9 and the testing is commenced. An observationmicroscope 22 is disposed between the base plate 2 and the upper plate 4for setting a relative position between the semiconductor wafer 9 andthe contact needles 21.

In the region above the receiving area 10 of the chuck, the upper plate4 has an observation opening 23. With that, it becomes possible, in amanner not shown in detail, to observe the reverse side of thesemiconductor wafer 9, which is on top, through this observation opening23 and through the opening 14, while the contact needles 21 engage thefront side of the semiconductor wafer 9.

As shown in FIGS. 3a and 3 b, it is also possible to design thereceiving area 10 of the chuck 8 in such a manner, that thesemiconductor wafer 9 can be inserted from above and locked. The needleholders 20 can then be disposed on the upper plate 4, the contactneedles 21 then engaging the semiconductor wafer 9 from above.

FIGS. 4a and 4 b shows the possibility of using a tester card. Thecontact needles 21 are fastened on a tester card. The tester card isfixed to the base plate 2 via an adapter 24. Accordingly, the contactneedles 21, the details of which are not shown, engage the tester cardon the front side of the semiconductor wafer 9, which is on the bottom.At the same time, it is possible to observe the reverse side of thesemiconductor wafer 9 from above.

In FIGS. 5a and 5 b, a combined possibility of simultaneously contactingfront and reverse sides by means of contact needles 21, is shown. FIGS.6a and 6 b show the simultaneous contacting of the front and reversesides by means of contact needles 21 and a simultaneous use of a testercard. In FIGS. 5a- 6 b, a microscope bridge 25 over the upper plate 4 isshown, on which the observation microscope, the details of which are notshown, can be fastened.

What is claimed is:
 1. An apparatus for testing semiconductor structureson a top side of a semiconductor wafer wherein the semiconductorstructures are chips and contact islands are provided on the chips onthe top side of the wafer, and a bottom side of the semiconductor waferis exposed during testing, the apparatus comprising: needle holders forholding contact needles for contacting the contact islands of the chipsto effect electrical connection for testing; a support structuresupporting the needle holders; a chuck, mounted on said supportstructure, for holding the semiconductor wafer in a receiving plane withthe top side of the semiconductor wafer facing in a downward directionsuch that respective ones of the contact needles are disposed beneathand in contact with respective ones of the contact islands; the chucksupporting the semiconductor wafer with the bottom side of thesemiconductor wafer facing in an upward direction exposed so as topermit optical inspection thereof from above; a positioning device foreffecting relative movement of said chuck with respect to said contactneedles to effect alignment of said contact needles with a respectiveone of the chips; and an infrared observation device disposed outsidesaid support structure and above the bottom side of the wafer to conductthe optical inspection.
 2. The apparatus of claim 1, wherein said chuckhas a chuck member defining an opening and a receiving area foraccepting the semiconductor wafer at a position aligned with saidopening such that the top side of the semiconductor wafer has saidcontact islands in contact with said contact needles and the bottom sideof the semiconductor wafer is exposed for the optical inspection viasaid opening.
 3. The apparatus of claim 1, wherein said positioningdevice comprises an x-y positioning stage supporting said chuck on saidsupport structure.
 4. The apparatus of claim 1, wherein said chuckincludes a fastening device for holding said semiconductor wafer bymeans of at least one of mechanical pressure or vacuum differentialpressure.
 5. The apparatus of claim 1, wherein: said chuck has a chuckmember defining an opening and a receiving area for accepting thesemiconductor wafer at a position aligned with said opening such thatthe top side of the semiconductor wafer has said contact islands incontact with said contact needles and the bottom side of thesemiconductor wafer exposed for the optical inspection; said chuckincludes a vacuum fastening device for holding said semiconductor waferin said receiving area including: said chuck member having a vacuumsealing surface in said receiving area whereat a portion of saidsemiconductor wafer is seated; said vacuum sealing surface defining asuction groove which is sealed by seating of said semiconductor wafer;and means for connecting said suction groove to a vacuum source.
 6. Theapparatus of claim 1, wherein said positioning device is disposed belowsaid chuck.
 7. The apparatus of claim 1, further comprising: spacermembers mounted on said positioning device and supporting said chuckspaced from said positioning device; said chuck having: a chuck platemember having a receiving area for accepting the semiconductor wafer anddefining an opening, said receiving area positioning the semiconductorwafer aligned with said opening such that the top side of thesemiconductor wafer has said contact islands in contact with saidcontact needles and the bottom side of the semiconductor wafer exposedfor the optical inspection; and external brackets disposed on opposingsides of said receiving area and connecting said chuck plate member tosaid spacer members.
 8. The apparatus of claim 1, wherein: said chuckhas a chuck plate member having a receiving area for accepting thesemiconductor wafer and defining an opening, said receiving areapositioning the semiconductor wafer aligned with said opening such thatthe top side of the semiconductor wafer has said contact islands incontact with said contact needles and the bottom side of thesemiconductor wafer exposed for the optical observation; said receivingarea includes an annular seat around the opening, at least a portion ofsaid annular seat being a vacuum sealing surface whereat a portion ofsaid semiconductor wafer is seated; said vacuum sealing surface defininga suction groove which is sealed by seating of said semiconductor wafer;and means for connecting said suction groove to a vacuum source.
 9. Theapparatus of claim 1 further comprising: said positioning devicecomprising an x-y positioning stage mounted on said support structure; aspacer member supporting said chuck on said x-y positioning stage at avertical distance above the x-y positioning stage; and an observationmicroscope for,observing alignment of said contact needle with saidcontact islands, said observation microscope being disposed below saidchuck, beneath said top side of said wafer, and higher than the x-ypositioning stage wherein said spacer member supports said chuck abovesaid observation microscope.
 10. The apparatus of claim 1 wherein: saidsupport structure includes a fastening plate having mounted thereon saidneedle holders for holding said needles contacting the contact islandson the top side of said semiconductor wafer to effect said electricalconnection for testing; said support structure includes a receivingplate supported on receiving plate spacers mounted on said fasteningplate; and further needle holders are provided, mounted on saidreceiving plate, for holding further needles for contacting the bottomside of the semiconductor wafer.
 11. The apparatus of claim 1, whereinsaid chuck includes a mechanical fastening device for holding saidsemiconductor wafer.
 12. The apparatus of claim 11, wherein: said chuckhas a chuck member defining an opening and a receiving area foraccepting the semiconductor wafer at a position aligned with saidopening such that the top side of the semiconductor wafer has saidcontact islands in contact with said contact needles and the bottom sideof the semiconductor wafer exposed for the optical inspection; and saidmechanical fastening means includes: at least one stop on said chuckmember for engaging an edge portion of said semiconductor wafer; asliding block slidably mounted in said chuck member to slide into saidreceiving area to engage another edge portion of said semiconductorwafer; and a biasing device for biasing said sliding block into saidreceiving area to engage the another edge portion of the semiconductorwafer to press the edge portion of the semiconductor wafer against saidat least one stop.
 13. The apparatus of claim 7, wherein: said receivingarea includes an annular seat around the opening, at least a portion ofsaid annular seat being a vacuum sealing surface whereat a portion ofsaid semiconductor wafer is seated; said vacuum sealing surface defininga suction groove which is sealed by seating of said semiconductor wafer;and means for connecting said suction groove to a vacuum source.
 14. Theapparatus of claim 13, wherein said means for connecting said suctiongroove to a vacuum source includes a vacuum duct passed through at leastone of said external brackets and at least one of said spacer members.15. An apparatus for testing semiconductor structures on a top side of asemiconductor wafer wherein the semiconductor structures are chips andcontact islands are provided on the chips on the top side of the wafer,and a bottom side of the semiconductor wafer is exposed during testing,the apparatus comprising: needle holders for holding contact needles forcontacting the contact islands of the chips to effect electricalconnection for testing; a support structure supporting the needleholders; a chuck, mounted on said support structure, for holding thesemiconductor wafer in a receiving plane with the top side of thesemiconductor wafer facing in a downward direction such that respectiveones of the contact needles are disposed beneath and in contact withrespective ones of the contact islands; the chuck supporting thesemiconductor wafer with the bottom side of the semiconductor waferfacing in an upward direction exposed so as to permit optical inspectionthereof from above; a positioning device for effecting relative movementof said chuck with respect to said contact needles to effect alignmentof said contact needles with a respective one of the chips, saidpositioning device comprising an x-y positioning stage mounted on saidsupport structure; a spacer member supporting said chuck on said x-ypositioning stage at a vertical distance above the x-y positioningstage; an observation microscope for observing alignment of said contactneedle with said contact islands, said observation microscope beingdisposed below said chuck, beneath said top side of said wafer, andhigher than the x-y positioning stage wherein said spacer membersupports said chuck above said observation microscope; and an infraredobservation device disposed above the bottom side of the wafer toconduct the optical inspection.
 16. The apparatus of claim 15 wherein:said support structure includes a fastening plate having mounted thereonsaid needle holders for holding said needles contacting the contactislands on the top side of said semiconductor wafer to effect saidelectrical connection for testing; said support structure includes areceiving plate supported on receiving plate spacers mounted on saidfastening plate; and further needle holders are provided, mounted onsaid receiving plate, for holding further needles for contacting thebottom side of the semiconductor wafer.
 17. An apparatus for testingsemiconductor structures on a top side of a semiconductor wafer whereinthe semiconductor structures are chips and contact islands are providedon the chips on the top side of the wafer, and a bottom side of thesemiconductor wafer is exposed during testing, the apparatus comprising:needle holders for holding contact needles for contacting the contactislands of the chips to effect electrical connection for testing; asupport structure supporting the needle holders; a chuck, mounted onsaid support structure, for holding the semiconductor wafer in areceiving plane with the top side of the semiconductor wafer facing in adownward direction such that respective ones of the contact needles aredisposed beneath and in contact with respective ones of the contactislands; the chuck supporting the semiconductor wafer with the bottomside of the semiconductor wafer facing in an upward direction exposed soas to permit optical inspection thereof from above; a positioning devicefor effecting relative movement of said chuck with respect to saidcontact needles to effect alignment of said contact needles with arespective one of the chips; an observation microscope for observingalignment of said contact needle with said contact islands; an infraredobservation device disposed above the bottom side of the wafer toconduct the optical inspection; said support structure including afastening plate having mounted thereon said needle holders for holdingsaid needles contacting the contact islands on the top side of saidsemiconductor wafer to effect said electrical connection for testing;said support structure including a receiving plate supported onreceiving plate spacers mounted on said fastening plate; and furtherneedle holders, mounted on said receiving plate, for holding furtherneedles for contacting the bottom side of the semiconductor wafer.